A post-nominal is the short form of qualification after your name. An example might be PhD or CPA. In the US they often begin with the letter "C" meaning certified.
It has come to my attention that your attitude towards member of management is not very good. You do not repect and you answer back. This is not values we live in this store.
Sympathy letters are personal, so say what you feel. It may be easier to buy a with sympathy card and then to add your own message. I guess if I were to do a letter i'd be sending my condolances to...